Method for dismantling electronic products containing cathode-ray tubes and for recycling the materials

ABSTRACT

A method for dismantling electronic devices equipped with cathode-ray tubes and for recycling the materials, including stages, in which the casing is removed from the device, the detachable auxiliary device components are stripped from the tube, and the materials are cleaned and sorted. According to the invention, a point laser is used to form a groove at the splitting point, which is situated towards the front part, at a distance from the joint between the front part and the conical part, and a temperature difference is created on the different sides of the said groove to ensure the splitting of the parts, and the components thus detached are used for further purpose. If desired, the laser source is also used to remove impurities, such a glue, labels, and similar, from the outer surface of the tube.

The present invention relates to a method for recycling cathode-raytubes and particularly for processing them after they have been takenout of use, in such a way that the raw materials are fully recovered.

Very large numbers of cathode-ray tubes (CRTs) are used in bothtelevisions and in computer displays. These are obviously replaced at acertain rate and it has been estimated that, on a European scale, 150000 tonnes of CRTs are scrapped annually, the number even in Finlandbeing 2000 tonnes annually, corresponding to approximately 250 000 CRTs.

When CRTs are scrapped, an attempt is made to recover all the usablematerials. In addition, an attempt is made to ensure that the recoveredmaterials are as clean as possible, which naturally makes their furtherusability and value as great as possible.

Instead of crushing CRTs, other methods too, which aim to give a betterend result, are used in scrapping is aimed at. Examples of these aredisclosed in the German patent application 4205404 and patentpublication 4234706, These disclose that a resistance wire is attachedto the tube in the area between the front and the conical rear part, thewire is heated, so that it violently heats the tube under it, crackingit and permitting it to be divided into two parts along the crack.

German application 3901842 in turn discloses the use of a high-pressurewater jet for cutting the tube into parts.

Further, the German publications 3901842 and 4003497 disclose the use ofa mechanical, water-cooled cutting blade for cutting tubes into parts.The latter publication also discloses that the CRT can be simplycrushed.

In addition, several methods are known, in which the lead solderingbetween the conical portion and the front part of the CRT is heated witha laser ray, allowing the part to be separated from each other.

In crushing, it is impossible to recover clean material. In addition,methods that use water for cutting or cooling have the drawback ofcreating an excess of water, which mixes with the cutting powder andcreates a mess. In any case, the water must be removed to allow furtherprocessing.

The glass of the front of the CRT must not contain any lead, if it is tobe able to be recycled for certain purposes. If the front is completelyclean when it is recovered, it will naturally be very much more valuablethan mixed waste. The aforementioned separation methods based on laserrays have the drawback that the said joint includes lead or is formed bylead, so that when the said methods are used the result is glass of verylittle value.

The conical portion of a CRT and its protruding rear part are of leadglass, which is used to keep the electromagnetic radiation entirelyinside the tube. The front part, on the other hand, is of conventionalglass. Colours require the use of coatings that luminesce in electronradiation, thus creating the colours. In addition, a CRT has both insideand outside various metal components, such as deflector coils, grids,and similar.

The Japanese company Matsuhita has developed a robotized system, whichcan dismantle televisions at a rate of about 50 seconds/device. Themethod is disclosed in U.S. Pat. No. 6,186,848. The most importantfeatures of the said patent are: the device to be dismantled is placedon a conveyor, which takes it to a sloping table where the protectivecase of the rear part of the device is removed, a powerful air jet isthen used to clean the mechanism and a U-shaped opening is cut in theside panel. Through this, the steel band protecting the joint betweenthe front and the conical portion of the CRT is then heated inductivelyand pushed off mechanically.

After this, the base of the metal band and the glue on it are brushedaway and the components of the CRT are cut off mechanically using adiamond disc and heated so that the thermal tension detaches thecomponents from each other. The other components are graded, crushed,and recycled to provide parts that are as clean as possible.

The said method requires the work of five people and six robots andnaturally also conveyors. The method described above uses separatesensors, of which there are several, to measure sizes and distances.

The present invention is intended to achieve a method, the use of whichavoids the drawbacks according to the prior art The intention is also tocreate an automatic method that will recover the recyclable material ina clean form.

The aforesaid and other benefits and advantages of the invention areachieved in the manner described as characteristic in the accompanyingClaims.

In the following, the invention is examined, without in any wayrestricting it, with reference to the accompanying schematic drawings,which show various specific features of the invention.

Thus:

FIG. 1 shows a practicable general arrangement of a working environmentfor applying the procedure according to the invention;

FIG. 2 shows one well-regarded procedure for detaching the front panelof a display terminal or television device containing a cathode-raytube;

FIG. 3 a shows how a groove is machined in a CRT with a laser, forsplitting;

FIG. 3 b shows in turn one procedure, by means of which the tube iseasily split along the groove.

FIG. 1 thus shows schematically an example of a workplace, in which, forexample, televisions or display terminals are dismantled. Thus, theactual conveyor line, along which the televisions or similar to bedismantled travel, is marked in the figure with the arrow 1. The devicesto be dismantled arrive at this line from the side along the schematicconveyor 2. The number 3 refers to conveyors, on which boxes travel,into which the dismantlers 4 collect the suitably sorted detachedcomponents. After detaching, the cases are lifted back onto theconveyors 5 and 6, from which they transfer to the transverse conveyor 7to be taken to crushing and other further processing.

The boxes filled with detached components are transferred to furtherprocessing on the transverse conveyor 9. The CRTs without their casesare transferred to further processing in the direction of the arrow 10.The devices to be dismantled are marked in FIG. 1 with the referencenumber 8.

The following is a brief description of one example of a processaccording to the invention. A television and a CRT computer displayterminal is generally assembled with screws, so that the frame and rearpart of the tube are screwed together at four points to create an entitycomprising the casing and shell of the device. According to the methodnow developed, the device containing the CRT is taken from the conveyor,attached by its CRT with a suction pad, which is not shown in detail inFIG. 1, but which is shown by the circle 11 in the centre of the device8, the rear casing is removed, as described later, the front casing isremoved downwards, so that the CRT with all its electronic devicesremains attached to the suction pad holder. The suction pad holdershould have a sufficiently large diameter to give a sufficient retentionmoment to allow, among other things, the deflector coils to be twistedoff the thin neck of the tube.

In the method now developed, the said screws can be sought inductively.This station is shown in FIG. 1 by broken lines as a block 12. If aninduction heating coil with a sufficiently high frequency is moved nearthe television or CRT, the coil begins to take more current when aferro-metallic component is nearby. The said detector is thus guided bya technique that is, as such, known, even closer to the ferro-metalliccomponent and heats it, for example, in the station 12, thus melting theplastic component surrounding it. If all the, for example, fourattachment screws are heated simultaneously, the components that thescrews hold together can be lifted apart from each other, so that therear and front panel of the casing are separated. This work stage isperformed by the dismantlers 4 immediately after the heating, when theysimply lift the rear part of the casing detached from the device ontothe conveyors 5 and 6.

The other small parts that are detached from the revealed mechanism aresorted in to boxes, which are underneath the belt Once the box is full,the dismantler presses a button and the box leaves for emptying 9 and isautomatically replaced by a new empty box.

After this, it is also wished to dispose of the front part of thecasing, which is usually a plastic component too. For this purpose, theseries of stages shown in FIG. 2 can be carded out at the dismantler'sworkstation. At the right-hand side of FIG. 2 is the situation in whichthe device, which is attached to a suction pad 11 and has its rear partremoved, in on the work table. First, the suction pad device 11 is usedto lift the device to the upper position, stage II, in which grip means13 grip it and hold it raised. The front part 14 of the casing remainson the table. In stage III, the suction pad device releases its grip onthe CRT and the arm of the suction pad device drops beneath the worksurface. In this stage, the front part 14 of the casing can be simplypushed aside onto the conveyors 5 and 6 of FIG. 1.

Stages IV and V show how the CRT, from which the casing has now beenremoved, is lowered from the support of the grip means 13. The CRTtravels on to the next stages. From now on, the CRT by itself is markedwith the reference number 15.

The next stage is the removal of the metal band that protects the jointbetween the front and rear parts of the CRT and to which other auxiliarydevices may also be attached. If desired, the location of the band canalso be sought inductively, in which case the heated and stretched bandis easy to remove. The removal can be done manually or automaticallyusing a robot-like device.

The work stages continue with the cleaning of the rest of the CRT, whichis already cleaned of its casing and band. Under the band there isgenerally a layer of glue, which, according to one embodiment of thisinvention, is removed with a laser device that provides a 2-3-cm widefan-shaped light beam, which burns the glue layer into a state in whichit can be removed with a brush or a blast of air. Next, the same or asimilar laser device uses an inductive detector or a photo-opticalreflection sensor to seek for various adhesive labels, which are removedby a fan laser in the same way as above.

At this stage, the outside of the CRT 15 is clean and the differentglass grades of the front and conical part of the CRT can be separatedin the next stage.

Thus after this a laser device, which is in this case a point laser 16,shown in FIG. 3 a, travels around the CRT, heating and removing materialfrom the CRT, thus forming a small groove 18 around it. In practice, thelaser device 16 is usually stationary while the CRT 15 rotates.

If suitable parameters are selected, the CRT will split naturally,without any further measures. Thus, in practical tests it has beenobserved that by using a laser beam with an output of 1200 W or more,for example 1500 W, and a speed at which the beam moves around the CRTduring this stage of less than 3 m per minute, the CRT will splitautomatically, without the possible heating/cooling measures describedlater. Particularly the direction or other parameters of the laser beamcan be adjusted to create a specific temperature gradient on thedifferent sides of the groove, thus ensuring splitting.

FIG. 3 b shows how the CRT 15 is divided into two parts along thisgroove 18, if it is wished to assist the splitting or if it must beassisted. This takes place by creating a large temperate difference oneither side of the groove 18, which will split the CRT 16 along thegroove 18. Thus, after the laser treatment described above, usuallyimmediately after it, compressed air is blown through a vortex pipe,that is as such known, on the different sides of the groove formed bythe laser. According to a known principle, the compressed aid fed intothe vortex pipe 17 divides into two air flows, with one end emitting hotair and the other cold air. This is a simple way of creating atemperature difference on the different sides of the groove 18 formed bythe laser. This temperature difference is usually enough to split theCRT along the said groove. Sufficiently rapid cooling/heating can becreated by using several vortex pipes.

Compressed air blown through the vortex pipe 17 at a pressure of 7 barwill already create a temperature difference of more than 100° C. whilea greater pressure will give a temperature difference of as much as 170°C.

It is obvious that the temperature difference can be created in manyother ways too. Thus it is possible to use conventional cold or hot airjets, or even a separate laser device to create the temperaturedifference.

Once the CRT 15 has been divided into two parts and its metal componentsremoved in ways that are, as such, known, manually or using a robot, thefluorescent powder is brushed and sucked off with an air flow frominside the CRT and then after this the aluminium oxide layer is brushedoff the sides with a power brush. In the method now being described, thealuminium oxide adheres to the said brush as abrasive particles, soforeign substances are mixed with the system as little as possible.

After this, the other detached metal components are separated with theaid of inductive heating and a thermal detector based on infraredradiation. Using a combination of these, the various metallicsubstances; ferromagnetic substances, and different heating and parts ofaluminium and copper can be automatically sorted separately onto thebelt.

The method differs significantly from the methods described previously.In this case, a laser is used, according to one embodiment, for twodifferent purposes; for removing material from a fixed point (the groove18) and, if desired, also for removing material (adhesive labels andsimilar) from a base without damaging it. If inductive heating is used,it can be used both to reveal a metal and to melt plastic from aroundmetallic attachments, and also for detaching the band of the CRT and,together with an infrared thermometer, for sorting metals.

The conical part of the CRT 15 generally includes a graphite and/ormetal-oxide coating, which is used to prevent the electron beam fromescaping. One well proven way of removing this coating and cleaning theglass is to immerse the conical part of the CRT in a vibrating grindingmachine for the removal. According to the invention partly fluorescingcrushed glass is used for cleaning, a 0.5-2.0-mm crushed fraction madeform part of the same CRT being used as the crushed material. Thecrushed glass together with the graphite, ground off label residues, andmetal oxides are led to separation, for example, to a cyclone separatorand bag filter, and are then returned to the vibrating grinding machine.Instead of a fluidizing vibrating grinding machine, blasting with thesame crushed glass can naturally also be used.

Working on CRTs with lasers involves special problems that do not arisein normal glass cutting. The problems are the porosity of the jointbetween the panel glass and the conical glass, the asymmetrical shape ofthe periphery, variations in the thickness of the glass and in the glassgrades, and other impurities in the joint. Thus, extensive tests haveshown that the glass should be grooved with a laser mainly 8-15 mm fromthe joint, on the panel glass (the tube font) sides to ensure thecleanness of the front glass and that this is preferably heated with thelaser in the de-focus position, so that the temperature difference isover 120° C. and that after this it is cooled symmetrically with avortex pipe travelling on at least two sides. According to the testsmade, the preferable laser output is 900-800 W and the preferable speedabout 3.5 m/min.

According to the present invention, the inductive heater is also usedunder robot control to reveal the heated screws, which are heated somuch that the plastic melts around them and the screwed joint can bepulled apart using a reasonable amount of force.

Using this procedure, human work power can be minimized, the number ofvarious sensors can be reduced, and the same devices can be used fordifferent tasks. According to the invention, dismantling can take placeeither entirely using a human workforce, or be fully or partlyautomated.

An essential part of the invention is the fact that the devices used areessentially only a laser device, with two different functions, andinductive heaters, as well as an infrared camera and a sorting robotthat it guides, as well as preferably, as an important sub-factor a“vibrating grinding machine”, in which fluid zing crushed glass is usedto clean the conical part of the CRT, or else the same cleaning can beperformed using crushed glass blasted with an air flow.

In this way, the plastic components are separated, the glasses aresorted into two classes, and the metals; iron, aluminium, and copper,and the circuit boards are sorted into different classes. After this,these are processed using normal crushing and sorting methods, whichare, as such, known from scrap processing.

1. A method for dismantling electronic devices equipped with acathode-ray tube and for recycling the materials, which includes stages,in which the casing of the device is removed, the detachable auxiliarydevice components are stripped from the tube, and the materials arecleaned and sorted, characterized in that a point laser is used to forma groove at a splitting point, which is situated towards the front part,at a distance from the joint between the front part and the conicalpart, the front part, and to cause a temperature difference on thedifferent sides of the said groove, in order to ensure the splitting ofthe parts, and the clean components thus separated from each other areused for further purposes.
 2. A method according to claim 1,characterized in that the laser source is also used to removeimpurities, such as glue, labels, and similar from the outer surface ofthe tube.
 3. A method according to claim 2, characterized in that aso-called fan laser or the de-focus setting of the laser is used toremove the impurities.
 4. A method according to claim 1, characterizedin that an inductive heating device is used to both search for metallicelements and to heat them.
 5. A method according to claim 1,characterized in that a laser beam, with an output of more than 1200 Wand the speed of movement of the beam over the tube is less than 3 m perminute, is used to make the splitting groove.
 6. A method according toclaim 3, characterized in that the fan, or de-focus laser is also usedto heat the tube, after the splitting groove has been made, especiallyin the immediate vicinity of the groove, in the area of one side of thegroove.
 7. A method according to claim 4, characterized in that the sameinductive heating element is used automatically to search for and heatthe said metal components requiring to be heated.
 8. A method accordingto claim 1, characterized in that the split parts of the tube are thencleaned, using, as the grinding material, the material that is obtainedby crushing parts of a tube that is similar to the tube to be cleaned.9. A method according to claim 4, characterized in that a frequency of400-1000 kHz is used in the inductive heating device, when searching forand heating screws, and 200-600 kHz when heating the band of the tube.10. A method according to claim 1, characterized in that the temperaturedifference is created on the different sides of the groove by using oneor several vortex pipes, the hot air jet of which is directed to oneside of the groove and the cold air jet to the other side.
 11. A methodaccording to claim 1, characterized in that a temperature difference ofat least about 120° C. is created on the different sides of the groove.12. A method according to any of the above claims, characterized in thatinductive heating at a standard output and the measurement of thetemperature of the parts using a device based on infrared light are usedto sort the parts, particularly the metal parts, obtained from thedismantling of the cathode-ray tube.